Clonal diversity and epidemiological characteristics of Staphylococcus aureus: high prevalence of oxacillin-susceptible mecA-positive Staphylococcus aureus (OS-MRSA) associated with clinical isolates in Brazil.

Mariana Andrade-Figueiredo,Tereza Cristina Leal-Balbino

doi:10.1186/s12866-016-0733-4

Mariana Andrade-Figueiredo, Tereza Cristina Leal-Balbino

Open Access

https://doi.org/10.1186/s12866-016-0733-4

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Journal: BMC microbiology	Publication Date: Jun 21, 2016
Citations: 73	License type: CC BY 4.0

Affiliation: Fundação Oswaldo Cruz

Abstract

BackgroundStaphylococcus aureus is the major cause of global and nosocomial infections with a significant impact in hospitals worldwide. Our objective was to investigate clinical and molecular characteristics of S. aureus isolates causing infections in patients admitted to hospitals from Recife city, Brazil, and investigate the prevalence of oxacillin-susceptible mecA-positive S. aureus (OS-MRSA) in the region, as well as genetically characterize the isolates and compare with epidemic clones.ResultsWe characterized 89 isolates in total, 31 clinical methicillin-resistant S. aureus (MRSA) and 58 methicillin-sensitive (MSSA) isolates by PFGE, MLST, spa typing and SCCmec genotyping. Isolates belonging to international MRSA clones were present: Brazilian epidemic clone (BEC) (61 % of MRSA isolates), Paediatric (36 %), New York/Japan (3 %). Some MSSA isolates were related to MRSA clones: USA400-related (10 % of MSSA isolates), Berlin clone (2 %), Paediatric (14 %), New York/Japan (2 %) and Southwest Pacific clone (17 %). MLST revealed new sequence types (ST’s): ST2381, ST2382, and ST2383 and new spa types: 10548 and 10550. Among isolates phenotypically identified as MSSA by antimicrobial susceptibility assays, we verified 30 oxacillin-susceptible isolates, which exhibited the mecA gene, without mec complex amplification and were thus classified as OS-MRSA. We observed clonal spread of MRSA and MSSA, including OS-MRSA, within several areas of the main hospital investigated and closely related isolates between hospitals analyzed.ConclusionsThe results of this study suggest a possible spread of the strains in hospital environment that could be responsible for nosocomial infections. We documented the presence of several MRSA clones, as well as new MLST and spa types, that were responsible for severe infections in hospitalized patients. The finding of OS-MRSA isolates could have implications for therapy, because testing for mecA and PBP2a is not a routine procedure performed by clinical microbiology laboratories in Brazil and, as consequence, these isolates could be misclassified as MSSA. Our data alert to the necessity to develop more effective strategies for epidemiological control of S. aureus in order to avoid an increase of hospital infections provoked by this pathogen. We reinforce the use of genetic methods, in addition to phenotypic tests, for a precise identification of MRSA.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0733-4) contains supplementary material, which is available to authorized users.

Highlights

Staphylococcus aureus is the major cause of global and nosocomial infections with a significant impact in hospitals worldwide
The staphylococcal cassette chromosome (SCCmec) typing for Methicillin-resistant Staphylococcus aureus (MRSA) isolates showed that 19/31 (61 %) isolates were SCCmec type III, 11/31 (36 %) isolates were SCCmec type IV and a single isolate was SCCmec type II
Some clusters included several of the major international MRSA clones (Clusters A/B/C included Brazilian epidemic clone (BEC); Cluster D and F, USA800/paediatric clone (PC); Cluster E, USA400)

Summary

Introduction

Staphylococcus aureus is the major cause of global and nosocomial infections with a significant impact in hospitals worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) has become widespread in hospitals, causing both serious nosocomial and community-associated infections worldwide. Methicillin-sensitive S. aureus (MSSA), which generally is genetically more diverse than MRSA, remains an important cause of infection [1, 2]. Methicillin-resistance in S. aureus results from acquisition of the mecA gene, harbored on a mobile genetic element (MGE), staphylococcal cassette chromosome (SCCmec), which produces an alternative penicillin-binding protein (PBP2a) with a low affinity for β-lactam antibiotics [2, 3]. MRSA has been defined as S. aureus having the mecA gene or phenotypically showing resistance to oxacillin/cefoxitin. Some isolates carry the mecA gene but are susceptible to oxacillin/cefoxitin, referred to as oxacillin-susceptible MRSA (OS-MRSA), known as cefoxitin-sensitive MRSA, which have been reported worldwide [5,6,7,8]

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